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95 Yukon Rebuild Thread

The ABS doesn't care about the engine. Up till 96 the ABS was completely stand alone. As for the s to f conversion, do you have an intake yet? I've got one I want out of my way. And I also have a water in fuel drain valve out in the shop.
 
I'll take you up on the intake. I thought I was going to have to make a junk yard trip to get the lower half intake.

I put a rebuilt set of heads on the donor '94 and the lower intake didn't match up correctly - needed the truck to get to work so I had to spent a very late night shaving down the intake to match the angle on the heads. Shop said they made a mistake on the cores........ Yeah, the shop is no longer in business.

Thanks for the good news. If ABS is standalone I shouldn't have much trouble getting rid of it.

Does the ABS warning light on the dash come from the ECM? No signal from ABS system = no input to ECM = No light on dash ??
 
The ABS light signal comes from the ABS module. If you unplug it the logic module in the cluster may turn the light on, in which case you can pull the bulb out of the cluster.
 
Boost gauge is installed. On the highway at 1,900 RPM @ 70 mph I have about 4 psi of boost. On the overpasses, rpm's and speed stay steady and boost climbs to 6 psi. Tried a couple pedal to the metal rolling starts from about 35-40 mph, boost & rpms climb quickly until about 7 to 7.5 psi and 2,500 +rpms then BAM - boost drops to 0 psi and stays there until I get off the pedal. Is this from the ECM opening up the waste gate to prevent high EGT?
 
Tough to tell and suspect there is either fuel starvation of some kind, or the ECM is holding back for some reason. If the conversion to VIN F is not complete, this might play into it. Question: when WOT, what does the exhaust plume look like? And when the boost slams back to 0 psi while still WOT, what does the exhaust plume look like?

As a reference point, when I still had the GM-8, mileage for the same type of highway driving (actually, had a few more hills) was 21 - 22 mpg and psi's were 6 - 8 on flat sections. Rear is 3.73 and the exhaust was already modified (updated 3" down pipe, 2-1/2" crossover, and 4" back). RPM's are in the ~2200 range at 70 mph per the dash gauge (using the dash gauge is noted as not highly accurate).

From the observation of 1,900 RPM's at 70MPH, the Yukon might have 3.42's, so the stated mileage (from an earlier post) of 14 mpg is probably under its potential even if it is still using the EGR.
 
Checked tach for rpm's using GMTDScan Tech. Software shows actual about 200 rpm lower than tach - tach reads 2,100 rpm @ 70 mph. 3.42 by RPO code. Tires are oversized from stock, and I haven't check VSS buffer jumpers yet.

Have not started vin F conversion. Exhaust plume light black haze as boost builds. I didn't look after boost dropped to 0 - I was watching the gauge.
 
Boost should not drop to 0. It should drop back to 7-7.5PSI at WOT down here in Floriduh. The 6.5L should maintain roughly 1.5 atmospheres of pressure at WOT unless it detects REALLY high intake air temps at which point it will defuel to keep it from overheating the incoming air charge(roughly 300 degrees or so IIRC). And your cruise boost should be in the 1.5-3 PSSI range, 4 PSI is to much boost for cruising. Even my BURB with 4.10's only held 2-2.5 pounds of boost running 70 at around 2300-2400 RPM's. And when I had a Gear vendors in it which effectively gave me a 3.08 gear, I held about 1.5 PSI of boost at 70 turning around 1800 RPM's. Boost should spike up to aorund 8-10 PSI when you flat foot stomp it, and then drop back to the 7 or so range. I seen as high as 11 a couple of times with the updated PROM chip in my BURB, but the factory PROM only seen 10 a handful of times.
 
Jay has you on the right track- you need to watch for the smoke. If boost drops and you get an increase in smoke then you are still gettin fuel and something is killing your boost. If it gets cleaner then your fuel is getting cut back not supplying the energy, and boost is falling off as a result.

You might need to have someone drive behind you to see.
 
Must be a fuel issue. At WOT, I'm getting a black haze from the exhaust. When boost falls off, exhaust plume clears - no increase in black haze from over fueling.

Installing Walbro pump from Leroy's just moved to the top of the list. I'll but in in now using existing lines, new filter and check FFM.

I had my laptop connected on the drive home yesterday and logged a lot of snapshots with GMTDScan Tech. I'll dump these into a spreadsheet. Cruise numbers are in line with info from THEFERMINATOR, on the overpasses bost rises slowly to maintain speed to about 4 PSI and then drops back down after I clear the rise.
 
Good news is I have boost when cruising at speed on the highway, and the improvement in mileage is significant. Last mpg with new injectors, glow plugs and air filter box restriction removed was 14.1 mpg. After this weeks commuting with boost from the turbo I got 19.2 mpg !!!

Bad news is I still have a trouble with boost falling off. Did some slow throttle roll ons, highway speed and in 3rd gear on a fcountry road. Same results each time.

For RPM I'm correcting for tach off by 200 rpms (tach vs GMTDScan Tech) so RPM below are actual engine RPM's

Below 1,600 RPM no boost
Around 1,66 RPM + some boost but erratic - by 1,700 RPM steady boost 1.5 PSI
1,700 RPM to 1,800 RPM steady boost that rise with RPM At 1,800 RPM 2.5 PSI boost
1,800 RPM to 1,900 RPM steady boost that rises with RPM At 1,900 RPM 3.5 psi boost
1,900 RPM to 2,000 RPM boost build steady with rpm until I hit 2,000. At 2,000 or slightly aboe, boost drops to 0.
If I keep RPM's just below drop ooff I have steady boost just over 4 PSI.

By they way for all the members out there, I got to see the Fermanators '95 Suburban with LB7 and Allison transmission. WOW with a Holy Crap and You've got to be kidding me + a few expletives that can't be used in public. I've seen a few engine swaps , and it's been my experience that you always see where something didn't quite fit or a work around was needed. Not in his ! You pop the hood and it looks like the engine grew there. Except for the air filter box for a high flow filter and some blue silicone hose - it looks factory OEM Really good stuff.

Question For Members:
Leroy's Diesel Walbro pump goes in next weekend. Crawled under the trucvk and took a close look with pump in hand. Hookm up to the front hard line to the top of the pump looks pretty simple and there is plenty of play to move it around. Rear hard pines looks a little trickier with the barb fitting. I was think of looping a section of hose around the back of the pump with a 90 and barb going into the base of the pump with the barb pointing foward. Any Suggestions?
 
what throttle position were you at when you hit 2k?. my guess is you have a bad sensor, what are your boost and IAT reading on the scanner when it happens.
 
renaissance said:
Question For Members:
Leroy's Diesel Walbro pump goes in next weekend. Crawled under the trucvk and took a close look with pump in hand. Hookm up to the front hard line to the top of the pump looks pretty simple and there is plenty of play to move it around. Rear hard pines looks a little trickier with the barb fitting. I was think of looping a section of hose around the back of the pump with a 90 and barb going into the base of the pump with the barb pointing foward. Any Suggestions?
Click to expand...

Some will benefit by using a 90* barb fitting or a street ell and the straight barb. ALSO FYI Im stocking some very high quality 3/8" fuel hose now. Anyone interested let me know. Will go on site soon.
 
Finally got the Walbro lift pump installed. Fabricated a support bracket out of 1/4" plate and mounted it 002.JPG on the cross member. Bracket is offset to the front of the cross member, and everything is safely tucked away and protected from road debris by the bracket or cross member.
 
It is a tape (PTFE I think) rated for use with gas and diesel fuel. A Parker distributor for the plant gave me a roll a while back. I'll see if I can get some info on it.
 
Any codes?
Did you remove the snorkel out of the fender during intake duct cleaning? How is the air filter?

Again any vacuum in the fuel system from a plugged sock, etc. can "vapor lock" a diesel IP.

Also you can read codes out of the ABS unit. It might indicate an early front wheel bearing failure.
 
2 days driving to work with the Walbro pump, and so far so good. The engine seems to be running smoother at highway speeds and pulling a little stronger and a little less rpm drop when I hit the over passes.

Air cleaner intake thoroughly cleaned when I did the injectors and glow plugs. Air filter is OEM style K&N also thoroughly cleaned and re-oiled before install. I don't think sock is clogged - I had a nice steady stream of fuel running down onto my chest when I hooked up the Walbro pump.

Had a FSD failure and replaced with a Flight Systems one from Leroy's Diesel last week.

Still have intermittent fish bite when cruising at highway speed. Possibly improved with Walbro pump, but it could be wishful thinking. I'm leaning towards a sensor/control problem like Diesel Driver suggested for the loss of boost. Trying to track down a non-egr ECM for the EGR delete with the intake manifold I got from the Ferminator. The '94 donor has the oddball injection pump, so I can't swap them out.
 
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